O2 Sensors

GBS 90 SC

Registered User
After a complete engine rebuild, I discovered that the repair shop neglected to change the oxygen sensors located on the exhaust manifolds. The HG's were blown prior to the rebuild and I know the sensors need to be replaced. If these sensors are bad, can this cause the engine to run hotter than normal at highway speed? Is it possible that the engine is running too lean?
I have noticed engine knock when the engine is hot and I seem to be burning more gas than usual. Ideas?
 
Yes its possable that the O2's are bad but you mentioned 2 things that tell alot.
1. Youre running hotter than normal. That does indicate a lean condition causing elevated combustion chamber temps.
2. Youre using more fuel than normal. That tells me the comp is in open loop so the comp has detected a problem and is trying to compensate by richening the fuel mixture but the problem is a little bigger than it can handle.
When the comp is in open loop it is no longer using the O2 sensors so at this point they dont have anything to do with whats going on.
You didnt say anything about the car idleing high so right now I dont think the IAC has anything to do with it.
You could have a vac leak in the system somewhere.
Check it out thoroughly, something may be leaking.
Once you eliminate vac leaks we will go further into it.
Pull the codes and see what they say. Post the code #'s.
 
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Code #61 was found in continuos memory. We have also found that the wrong temp. sensor was used by the rebulider. I need to drive the car now that the correct sensor was installed and see how it runs.
What does this Code #61 mean? I don't see how this sensor can have anything to do with the engine running too rich though-
 
If the sensors were contaminated they could still switch but at a higher oxygen content. This would cause the computer to think it is running rich and compensate. With just a 10% compensation on the long term trim it could go as far as pushing a 13.5 A/F to 14.9. So, the oxygen sensors can cause some serious issues if they go bad but don't go completely out of range.

Aaron
 
Code 61=ECT sensor fault, or circuit grounded.
Its very possable that that is the whole problem.
If the comp cant get a reading from the ECT it will keep the comp in open loop causing rich mixtures.

Replace the ECT sensor with the PROPER one disconect battery to reset comp and try again. The car may run alittle rough until the comp relearns, just let it idle for awhile and it should smooth out.
 
Correction

Now the dealer that is working on my car has said that it is the Temperature Sendor and not the ECT Sensor that was the "wrong" part. Apparently this sendor is suppose to have a green insolater which it didn't. The dealer also told me that Code #61 could have been there for awhile and after resetting, it is now gone and is not a "hard code." (No codes now)

Can a wrong sendor actually make a temp gauge creep up when going down the highway? Eventhough it is in contact w/coolant, I don't see this having any impact on the EEC. I am still trying to figure out why I got the code to begin with. Maybe it happened when it was installed when the engine was rebuilt.
 
If the guage sender unit is not the proper one the temp gauge readings could be off making it look like the car is runing warmer or cooler than it really is.
If the ECT sensor is not the correct one the ECU would not get a correct reading and cause the comp to access wrong fuel and timing tables causing mixture problems.
Follow the link in a post I put up titled " Learn EEC-IV and Fuel Injection" for a very good explination of how it all works.
 
NOx failure

I just replaced my O2 sensors and it made a 23% inprovement
on the NOx test run at 25mph, which was just enough to get it to pass. This was the first time I have replaced the O2's.

I have a stock 1990 SC with 170k, with aod Lentech tranny.
 
Better safe than sorry...

I am going to go ahead and replace mine as well. Eventhough I'm not getting a code with the original O2 sensors, it seems like the right thing to do. I hope to have the car back tonight so that I can report back on Monday.
 
I should have replaced the oxygen sensors a long time ago. The car is running the way it should be and it is staying cool at the same time. I think the O2's were the answer and highly recommend that they be changed after HG failure. It is easy to do and the results are worth the price of the parts.
Thanks to all who have helped me solve my problem-
God's Speed, GB
 
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